1. Field of Invention
The invention relates to a running control apparatus and method.
2. Description of Related Art
According to a running control apparatus described in JP-A-9-323628, a brake that reduces rotation of a wheel is actuated when the inter-vehicle distance between a vehicle and a preceding vehicle (hereinafter referred to as an inter-vehicle distance) becomes equal to or less than a set value. Therefore, the vehicle can be reliably decelerated, and excessively close approach to a vehicle ahead can be avoided.
However, the above-identified running control apparatus actuates the brake without consideration as to whether a preceding vehicle is running in the same lane as the vehicle. Therefore, if the preceding vehicle is not running in the same lane as the vehicle, the apparatus may unnecessarily actuate the brake.
It is one object of the invention to avoid unnecessary actuation of a brake by a running control apparatus that controls the state of running of a vehicle based on a relative positional relationship between the vehicle and a preceding vehicle. This object can be achieved by implementing a running control apparatus and method according to the aspects of the invention described hereinafter. It should be understood that the technical features described in this specification and combinations thereof are not limited to the following embodiments. Furthermore, a plurality of features described herein do not have to be adopted altogether. The invention includes one or more of the various features used singularly or together.
According to one aspect of the invention, a running control apparatus and method controls a running state of a vehicle based on a relative positional relationship between the vehicle and a preceding vehicle running ahead of the vehicle in a preset area. It determines a probability that an object detected in the preset area is the preceding vehicle that is running ahead in the same lane as the vehicle. Then, the invention actuates a brake that retards rotation of a wheel of the vehicle when a relative positional relationship between the vehicle and the preceding vehicle indicates that the vehicle should be decelerated, wherein the relative positional relationship between the vehicle and the preceding vehicle indicating that the vehicle should be decelerated includes a state in which a the determined probability is equal to or greater than a preset probability.
In the running control apparatus described as above, the brake is actuated if the probability that a body detected in the preset area is a preceding vehicle running in the same lane as the vehicle (hereinafter, simply referred to as xe2x80x9csame-lane probabilityxe2x80x9d) is equal to or greater than a set probability value. When the same-lane probability is low, the brake is not actuated. Therefore, unnecessary operation of the brake can be avoided. A running control apparatus and method described above may also prohibit actuation of the brake if the same-lane probability is less than the set probability.
The relative positional relationship between the vehicle and a preceding vehicle may be represented by the relative position of the preceding vehicle to the vehicle as well as the changing speed of the relative position, the changing acceleration thereof, or specific data that cause such change, for example, the speed of the vehicle or the preceding vehicle, the acceleration thereof, etc. The relative position may be expressed as a point in a plane coordinate system defined by a direction parallel to a predicted running line of the vehicle (which may be a straight line extending through the center of the vehicle in the longitudinal direction or a curve determined taking into account the steering angle or the running speed, the yaw rate, etc.) and a direction perpendicular thereto (lateral direction of the vehicle). The inter-vehicle distance refers to the distance between the vehicle and a preceding vehicle. If the predicted running line is a curve, the inter-vehicle distance may be expressed as a straight-line or a curve. Furthermore, if the predicted running line is a curve, the relative position may be expressed as a point in an orthogonal plane coordinate system obtained by developing the curve into a straight line. Based on the relative position, it is possible to determine whether the preceding vehicle is located in a specific area that is predetermined in an orthogonal plane coordinate system, or to acquire a probability that the preceding vehicle is located in the specific area. The result of such determination and the probability may represent the relative positional relationship. A value obtained by dividing the inter-vehicle distance by the running speed of the vehicle may also represent the relative positional relationship.
The same-lane probability determining process may include determining whether an object detected in the preset area is the preceding vehicle so as to acquire a probability that the body determined as a preceding vehicle is running in the same lane as the vehicle. This preceding vehicle determining process may include determining whether the object detected in the preset area is in a moving state or a stationary state. The moving state determining process may determine whether the object body is in a stationary state based on, for example, the running speed of the vehicle and a relative speed between the vehicle and the object body. If an approaching speed, that is, a kind of the relative speed, is greater than or equal to a set approaching speed (which may be either a constant value or a value that is set based on the running speed of the vehicle), or if the relative speed is substantially equal to the running speed of the vehicle (e.g., if the absolute value of a difference between the aforementioned two speeds is less than or equal to a positive set speed difference value), it may be determined that the object body is in a stationary state. The preceding vehicle determining process may include discriminating whether the preseecinf vehicle is at least one of a vehicle running on the opposite lane and a vehicle passing an intersection. The process for determining whether a vehicle is running on the opposite lane is operable to determine that a target body is an oncoming vehicle if the approaching speed of the vehicle with respect to the target body is greater than the running speed of the vehicle by at least a set approaching speed. The process for determining whether a vehicle is passing an intersection is operable to determine that a target body is a vehicle running on the crossroad if, for example, the absolute value of the moving speed of the target body in a direction perpendicular to the predicted running line of the vehicle is greater than or equal to a set moving speed. The preceding vehicle determining process may include determining that the detected object is a vehicle (which may or may not include a two-wheeled vehicle) when the detected object has a size (at least one of the height and width) larger than a preset size, and determining that the detected object is not the vehicle when the detected object has a size smaller than the preset size.
The same-lane probability of a preceding vehicle may be determined, for example, based on a relative position of the preceding vehicle determined as mentioned above, that is, a relative position thereof in a direction perpendicular to a direction parallel to the predicted running line of the vehicle. That is, the smaller the deviation of the preceding vehicle from the predicted running line of the vehicle in a perpendicular direction becomes, the higher the same-lane probability becomes. Furthermore, as will be described later, the same-lane probability may be determined by dividing the area defined by the orthogonal plane coordinate system mentioned above into a plurality of areas, and correlating the individual divided areas and values of the same-lane probability so as to be pre-stored. In this case, the value corresponding to the area to which the relative position of the center point of a predetermined vehicle belongs may be determined as a same-lane probability. Furthermore, the value corresponding to the area to which the relative position of a point that represents the preceding vehicle, instead of the center point thereof, may also be determined as the same-lane probability. If a preceding vehicle is defined by a plurality of points within a single body, it is not always the case that all the points belong to a single area; rather, there are cases where the points belong to a plurality of areas. In such a case, the same-lane probability may be determined based on the values corresponding to the plurality of areas. For example, the mean value or an intermediate value of the values of probability corresponding to the areas may be determined as the same-lane probability. The same-lane probability may be a value determined taking into consideration a weighting, for example, a manner of weighting in which the weighting of the value corresponding to the area to which the center point of the object body belongs is made greater than the weighting of the values corresponding to the areas to which points in end portions of the object body belong. If, in a case where at least one of a plurality of areas is defined as a specific area, at least one of a plurality of points of a preceding vehicle belongs to the specific area, the value corresponding to that specific area may be determined as a same-lane probability.
According to another aspect of the invention, the braking system (deceleration device) of the running control apparatus is operable to actuate the brake to retard rotation of the wheel of the vehicle if a degree of a necessity to decelerate the vehicle, which is determined based on the relative positional relationship, is higher than a preset degree.
It is possible to determine the necessity for decelerating the vehicle, a degree of the necessity and the like based on the relative positional relationship between the vehicle and a preceding vehicle. The necessity for deceleration may be determined, for example, based on actual and desired relative positional relationships. The desired relative positional relationship may be, for example, a requested relative positional relationship intended by a vehicle operator, a set relative positional relationship predetermined based on safety, or the like. It is often the case that the requested relative positional relationship or the set relative positional relationship remains unchanged during one running control cycle. Therefore, the necessity for deceleration of the vehicle may be governed by the actual relative positional relationship between the vehicle and the preceding vehicle. The requested relative positional relationship may be set, for example, by an operation performed by the operator. The operator sets a desired inter-vehicle distance, a desired inter-vehicle time, etc., for example, by operating an operating member (a switch, a touch panel, etc.). The brake may be actuated if deceleration is required and the same-lane probability is greater than or equal to a set probability. Alternatively, the brake may be actuated if the degree of the necessity is greater than or equal to a set degree and the same-lane probability is greater than or equal to a set probability.
Assuming that the desired relative positional relationship is a requested inter-vehicle distance requested by a vehicle operator, if the actual inter-vehicle distance is less than the requested inter-vehicle distance, it can be determined that there is a necessity for deceleration. The greater the difference between the requested and actual inter-vehicle distances (requested inter-vehicle distancexe2x80x94actual inter-vehicle distance) becomes, the higher the necessity for deceleration is considered to be. Thus, the necessity for deceleration or the degree of the necessity can be detected based on the deviation, that is, positive/negative of a deviation obtained by subtracting the actual inter-vehicle distance from the requested inter-vehicle distance, or the magnitude of the absolute value of the deviation. The necessity for deceleration or the degree of the necessity may also be determined based on, instead of the deviation, a quantity related to the deviation, for example, a deviation ratio obtained by dividing the deviation by the requested inter-vehicle distance, or the like. According to the running control apparatus and method described herein, the possibility of unnecessary actuation of the brake can be further reduced.
As for the brake, it is desirable that the state of operation of the brake (for example, the amount of braking (hard versus soft)) be controlled to a state corresponding to the necessity. However, the invention is not limited to this. The brake may be actuated in a predetermined state when the necessity arises.
Furthermore, it is desirable that the brake be operable without an operation of a brake operating member performed by a vehicle operator.
According to another aspect of the invention, a running control apparatus may include a body detector that detects a body in the preset area in front of the vehicle. The set area may extend two-dimensionally, or three-dimensionally. The body detector may detect a body based on a state in which a reflection of electromagnetic waves emitted forward is received, for example, a laser radar device, or it may detect a body based on a video image that has been taken by, for example, a CCD camera.
The set area may be determined based on an area in which a body can be detected by the body detector. For example, the set area may be determined based on a common area between an area of the electromagnetic wave irradiation and an area that allows reception of reflected waves, or may be determined based on an area that allows the image to be taken by the CCD camera. Such an area that allows detection of a body is determined by the body detector or the like, and in some cases, may be determined by climate or the like as well. If the set area is a two-dimensional area, the area may be specified based on, for example, at least one of: (a) the angle of electromagnetic wave radiation in a horizontal direction, and (b) a shorter one of the distance of electromagnetic wave radiation and the distance of reflected wave reception. If the set area is a three-dimensional area, the area may be determined based on, for example, (c) the angle of electromagnetic wave radiation in a horizontal direction, (d) the angle of radiation in a vertical direction, (e) a shorter one of the radiation distance and the reception distance, etc.
According to another aspect of the invention, the running control apparatus detects an actual deceleration of the vehicle. The braking system is operable to actuate the brake if a deceleration deviation-related amount is equal to or greater than a preset deviation-related amount, the deceleration deviation-related amount being related to a value obtained by subtracting the detected actual deceleration from a target deceleration determined based on a desired relative positional relationship and an actual relative positional relationship detected by the body detector.
In the running control apparatus described above, a target deceleration is determined based on the actual relative positional relationship and the desired relative positional relationship. The brake is actuated if the deceleration deviation-related amount related to a value obtained by subtracting the actual deceleration from the target deceleration is greater than or equal to the set deviation-related amount. It is appropriate to actuate the brake in case of excessive shortage of the actual deceleration with respect to the target deceleration.
The features described as above may be adopted independently of each other. More specifically, even if the same-lane probability of a detected body is smaller than a set probability, it is possible to actuate the brake in the case where the deceleration deviation-related amount is at least the set amount related to the deviation.
According to another aspect of the invention, if the relative positional relationship indicates that the vehicle should be decelerated, the braking system controls at least one of a driving device that supplies power to drive the vehicle and a power transmitting device that is disposed between the driving device and the wheel of the vehicle such that the vehicle is decelerated, prior to actuation of the brake.
In the above-described running control apparatus, the control of the driving device or the power transmitting device is performed before actuation of the brake if there arises a necessity to decelerate the vehicle. That is, the control of the driving device or the power transmitting device is performed prior to actuation of the brake. Therefore, the frequency of operation of the brake can be correspondingly reduced.
The aspect of the invention in which the control of the driving device or the power transmitting device is given a higher priority is, for example, an aspect in which if the necessity to decelerate the vehicle is low, the driving device or the power transmitting device is controlled, and in which if the necessity becomes higher than a set value, actuation of the brake is performed in addition to the control of the driving device or the power transmitting device, or instead of the control of the driving device or the power transmitting device.
Due to the control of the driving device, the driving torque transferred to the wheel is reduced (which includes being changed to a negative torque) so that the revolution speed of the wheel is reduced. Due to the control of the power transmitting device, the ratio between the revolution speed of the driving device and the revolution speed of the wheel is changed so as to reduce the revolution speed of the wheel. Such deceleration includes not only deceleration based on generally-termed engine braking, but also deceleration achieved by making the drive torque transferred to the wheel smaller than the running resistance torque.
If the driving device includes an engine, a control of reducing the output torque of the engine or the like is included in the aforementioned deceleration. If the driving device includes an electric motor, a control of reducing the output torque of the electric motor or the like (including the performance of regenerative braking by an electric motor) is included in the deceleration.
According to another aspect of the invention, the braking system is operable to control at least one of the driving device and the power transmitting device if the relative positional relationship meets a preset controlling condition, and the deceleration device is operable to actuate the brake if the relative positional relationship meets a brake actuating condition.
It is desirable that the controlling condition be set so as to be satisfied when the degree of necessity to decelerate the vehicle is lower as compared with the brake actuating condition.
According to another aspect of the invention, the running control apparatus permits or prohibits actuation of the brake based on at least one of a state of a brake control device that controls a brake operation state and a running state of the vehicle.
In this aspect, if actuation of the brake is prohibited, the brake will not be actuated even in a case where the relative positional relationship indicates that there is a necessity to decelerate the vehicle. It may be deemed undesirable to actuate the brake without a brake operation performed by a vehicle operator, that is, without the operator being aware of the brake actuation.
According to another aspect of the invention, the actuation of the brake is inhibited in at least one state of (a) a case where a value corresponding to a slip state of the wheel of the vehicle is equal to or greater than a set value, or a case where there is a high possibility that the value corresponding to the slip state of the wheel of the vehicle becomes equal to or greater than the set value, and (b) the brake control device is in a state in which actuation of the brake is undesirable. If the value corresponding to the slip state of the wheel of the vehicle is equal to or greater than the set value, there is a danger that, the wheels are brought into a locked state from a slip state by the braking operation. Even if the set state has not been currently reached, there is a danger that the braking operation may bring the wheels into the lock state from the slip state. It is, thus, preferable to prohibit the brake actuation.
It also is undesirable to actuate the brake in case of overheating of a brake liquid pressure actuator that is actuated when supplied with electric energy, or in the case of an abnormal state of the brake control device.
According to another aspect of the invention, the running control apparatus includes an alarm device which produces an alarm when actuation of the brake is prohibited by the brake actuation permitting/prohibiting device.
If the alarm device is provided, it is possible to notify a vehicle operator that actuation of the brake has been prohibited even though the relative positional relationship indicates that it is desirable to actuate the brake. Then the vehicle operator is able to perform an appropriate operation in response to the alarm. If braking is required, the operator is allowed to operate the brake operating member in accordance with the necessity.
According to another aspect of the invention, the deceleration device includes a brake control device which controls an operation state of a brake, and the brake control device includes a cruise control portion which controls an operation state of the brake in accordance with a necessity to decelerate the vehicle.
During a cruise control, a control is performed so that the relative positional relationship between the vehicle and a preceding vehicle continues to be a requested relative positional relationship requested by an operating person or a preset relative positional relationship.
According to another aspect of the invention, the brake control device includes an antilock control portion which controls the brake such that in a case where the brake is in an actuated state and where a value indicating a slip state of the wheel that is in a locked state is larger than a preset value even when a brake operating member is not operated by a vehicle operator, the slip state of the wheel is brought into an appropriate range.
In a case where an automatic braking brings the wheels into a locked state from a slip state even when no braking is performed by a vehicle operator, antilock control is started. As a result, even when the wheels in the slip state are brought into the locked state owing to an automatic braking during cruise control, deterioration of the running stability of the vehicle can be effectively avoided. Therefore, it is preferable to employ both the cruise control and the antilock control. It is further preferable to prohibit the cruise control upon the start of the antilock controlling.
According to another aspect of the invention, the running control apparatus includes a vehicle behavior control portion which controls at least one of the brake and the driving device, if a behavior of the vehicle is unstable as compared with a set state, such that the behavior of the vehicle is brought into an appropriate state.
In the running control apparatus described as above, it is preferable to prohibit the cruise control upon the start of the vehicle behavior control, as is done in the aforementioned case.
According to another aspect of the invention, a running control apparatus that controls a running state of a vehicle based on a relative positional relationship between the vehicle and a preceding vehicle running ahead of the vehicle in a preset area includes a control command value determination controller that determines a control command value related to deceleration of the vehicle based on the relative positional relationship. In addition, a brake controller controls a state of operation of a brake that retards rotation of a wheel in accordance with the control command value received from the control command value determination controller, and a control abnormality detector detects a control abnormality based on a logical consistency of contents of a plurality of pieces of information that include a piece of information transmitted between the control command value determination controller and the brake controller.
In the running control apparatus described above, a control abnormality is detected based on a plurality of pieces of information that include a piece of communication information. Control abnormalities are caused by mis-operations or non-operations of computers, actuators and the like, communication abnormalities, etc.
A control abnormality occurs, for example, if an actuator is not operated in accordance with a control command value, or if a control command value is not generated in accordance with a program, or if due to an abnormality of a sensor or the like, an actually occurring phenomenon related to the state of operation of the brake, the relative positional relationship between the vehicle and the preceding vehicle, etc., is not correctly detected, or if a content of control command information or a content of control result information is changed due to a communication mutation or the like.
A control abnormality can be detected if the contents of two or more pieces of information do not have a logical consistency. In this case, since the brake control device controls the state of operation of the brake in accordance with a control command value transmitted from the control command value determination controller, at least one of the two or more pieces of information may be the control command value transmission information. In that case, the control abnormality includes: (a) an abnormality that if there are a plurality of pieces of control command value transmission information, at least two of the pieces of transmission information do not have a logical consistency; (b) an abnormality that a piece of control command value transmission information and a sensor-detected value acquired by a computer or a piece of information generated by the computer, etc., do not have a logical consistency; (c) an abnormality that the content of a piece of control command value transmission information and the content of a piece of information sent back in accordance with an echo-back request do not have a logical consistency; etc.
More specifically, if a plurality of pieces of information received by the brake control device from the control command value determination controller include brake request information and information indicating a target deceleration, it may be determined that there is a logical consistency. If the pieces of information include brake request information and information indicating a target acceleration (deceleration of a negative value), it may be determined that there is a logical abnormality (a). Furthermore, if the information received by the brake control device includes brake request information, but the brake actuating force detected by a sensor is xe2x80x9c0xe2x80x9d, it may be determined that there is no logical consistency (b). If the control command value determination controller transmits brake request information to the brake controller, but the information sent back in accordance with an echo-back request does not include brake request information, it may be determined that there is no logical consistency (c).
If in addition to the echo-back request, the transmission of information detected by the brake control device or information generated thereby is requested, it is possible to detect whether there is a logical consistency between the information transmitted from the control command value determination controller and the information transmitted from the brake control device. For example, if, in a case where the brake control device transmits information indicating a state of a brake in-operation flag that is set during operation of the brake, and that brake inoperation flag transmitted from the brake control device is in a reset state although brake request information is transmitted from the control command value determination controller, it may be determined that there is no logical consistency.
Thus, with a construction in which a control abnormality is detected based on the contents of a plurality of pieces of information that include communication information, it becomes possible to discover a mis-operation or a non-operation of the brake in an early period, and to therefore improve reliability of the running control apparatus.
It is not essential that a control abnormality be detected based on a plurality of pieces of information containing control command value transmission information. That is, it is possible to detect a control abnormality based on a plurality of pieces of information that do not include control command value transmission information. For example, a control abnormality may be detected based on a plurality of pieces of information that include a sensor-detected value acquired by a computer or information generated by the computer.
The technical features described herein can be applied to a running control apparatus described in any one of the above-described aspects of the invention.
According to another aspect of the invention, a running control apparatus includes a control device which controls at least one of a driving device that drives the vehicle and a power transmitting device disposed between the driving device and the wheel of the vehicle in response to a control command value transmitted from a control command value determining controller, wherein a control abnormality detector detects the control abnormality based on the plurality of pieces of information containing information regarding communication among the control command value determining controller, the brake controller, and the control device.
For example, if information which commands a dshift is transmitted from the control command value determining device although a cruise control switch connected to the control device is in an off state (no cruise control is required), it may be determined that there is a logical abnormality.
According to another aspect of the invention, the brake controller prohibits actuation of the brake if the control abnormality is detected by the control abnormality detector.
If actuation of the brake is prohibited upon detection of a control abnormality, a mis-operation of the brake is avoided at an earlier stage. It is also possible to prohibit the control of the driving device or the power transmitting device as well as the actuation of the brake.
Furthermore, if a construction is provided in which an alarm is produced upon detection of a control abnormality, it becomes possible to notify a vehicle operator of occurrence of a control abnormality. Then the vehicle operator can perform, for example, a braking operation in accordance with the necessity.
According to another aspect of the invention, a running control apparatus controls a running state of a vehicle based on a relative positional relationship between the vehicle and a preceding object ahead of the vehicle in a preset area. The running control apparatus determines a probability that an object detected in the set area is the preceding object that is running ahead in the same lane as the vehicle, and a braking system operates a brake that retards rotation of a wheel of the vehicle when one of the relative positional relationship between the vehicle and the preceding object indicates that the vehicle should be decelerated, wherein the relative positional relationship between the vehicle and the preceding object indicating that the vehicle should be decelerated includes a state in which the determined probability is equal to or greater than a preset probability.
The object present in the preset area in front of the vehicle may be in a moving state, or may also be in a stationary state. The running control apparatus described herein may adopt any of the technical features described in any of the above-described aspects of the invention.